Shell plate, method for making a shell plate and a grinding mill

ABSTRACT

The invention relates to a shell plate, to method for making a shell plate and to a grinding mill for ore grinding. The shell plate is mountable to a shell of a grinding mill for grinding ore, said shell plate comprises a shell plate body having a first portion comprising a fixing surface for fixing the shell plate body to the shell and a second portion comprising a wear surface facing toward interior of the grinding mill, said first portion and said second portion forming a continuous shell plate body, the second portion comprises polyurethane such that the wear surface is made of polyurethane.

FIELD OF THE INVENTION

The invention relates to a shell plate, and more particularly to a shellplate as defined in the independent claim 1. The invention furtherrelates to a method for making a shell plate as defined in theindependent claim 12 and to a grinding mill as defined in theindependent claim 15.

BACKGROUND OF THE INVENTION

Grinding mills are used for processing hard solid material such thatlarge solid material is grinded into smaller pieces. Lifting bars assistin lifting the solid material that is being processed in the drum as itrotates and the shell plates' function is to protect the shell of thegrinding mill.

BRIEF DESCRIPTION OF THE INVENTION

The shell plate according to the invention, the method for making ashell plate according to the invention and the grinding mill accordingto the invention are characterized by what is stated in the independentclaims. The preferred embodiments of the invention are disclosed in thedependent claims.

The solid material is crushed in a drum shaped shell mounted forrotation about its central axis in the grinding mill. The axis of therotatable shell is generally horizontally arranged or slightly inclinedtowards one end in the grinding mill. The interior of the shell forms atreatment chamber and has a cylindrical wall. The inner surface of thechamber is plated with a lining for protecting the shell because thematerial to be processed is fed to the treatment chamber and grinding itcauses wear in the chamber. The interior wall of the shell is equippedwith lifter bars for lifting the material inside the shell along therotation so that as the shell rotates the shell plates lift up the solidmaterial along the inside wall of the shell to a point where gravitycauses the solid material to fall down inside the shell and by fallingdown the solid material is crushed. In order to protect the shell of thegrinding mill shell plates are arranged in between adjacent lifter bars.

Lifter bars as well as shell plates extend from one end of the drum toanother end and they are arranged in a short spacing adjacently alongthe cylindrical wall of the shell. The shell plates do not protrude fromthe shell wall as much as the lifter bars which assist in lifting thesolid material. The shell plates have an outer surface and comprise ashell plate body having a fixing surface for connecting the shell plateto the shell of the grinding mill. The shell plate body has an outersurface comprising a fixing surface to be arranged against the shell anda wear surface facing toward interior of the grinding mill. The shellplate body comprise a first portion and a second portion forming acontinuous shell plate body, said first portion comprises the fixingsurface which is arranged against the shell when connected to thegrinding mill.

The shell plate is mountable to a shell of a grinding mill for grindingore. The shell plate may be secured to the shell of the grinding millsuch that the adjacent lifter bars interlock the shell plate to itsplace or the shell plate may have a fixing element embedded to the shellplate which forms part of the fixing surface of the shell plate. Whenmounted to the shell the fixing surface is arranged against the shelland the shell plate is secured to the shell through the fixing elementin the shell plate or through adjacent lifter bars. When having a fixingelement the shell plates are mechanically fastened to the inner surfaceof the shell with fastening means such as a bolt connection through thefixing element. When the shell plate is installed to the shell of thegrinding mill the fixing surface of the shell plate body is facedagainst the inner surface of the shell of the grinding mill.

A grinding mill for ore grinding comprises multiple shell platesarranged to a shell of the grinding mill, the shell plates being asdescribed earlier. The shell plate is used in grinding mills havinggrinding energy per ton of ore of 1-30 kWh/t and preferably 3-20 kWh/t.The diameter of the grinding mill is 1-15 m, and most typically 1.5-10m. The length of the grinding mill in horizontal direction is between 1and 15 meter, and most typically from 2 to 8 m. Thickness of the shellof the grinding mill is 0.5-10 cm. Grinding mills can be for example SAGmills, AG mills, Ball mills, rod mills, scrubbers or regrinds.

The grinding mill comprises multiple lifter bars arranged to the shell,which the lifter bars comprise a lifter bar body having a fixing surfacefor fixing the lifter bar to the shell and a wear surface facing towardinterior of the grinding mill, the wear surface of the lifter bars andthe wear surface of the shell plates comprise polyurethane. The grindingmill is arranged to grind input material of which at least 80% hasparticle size between 0.1-300 mm, preferably 1-250 mm and mostpreferably 80-220 mm to grinded output material of which 80% hasparticle size between 0.02-3 mm, preferably 0.05-2.5 mm and mostpreferably 0.2-2 mm.

The grinding mill comprises a lifter bar arranged to the shell, whichthe lifter bar has a volume. The lifter bar further has an outer surfacecomprising a fixing surface to be arranged against the shell and a wearsurface facing toward interior of the grinding mill. The lifter barcomprises a lifter bar body having an outer surface conforming the outersurface of the lifter bar and a fixing element for connecting the lifterbar to the shell of the grinding mill. The lifter bar body furthercomprising a first portion and a second portion forming a continuouslifter bar body, the fixing element is embedded to the first portionsuch that it forms part of the fixing surface of the lifter bar. Thesecond portion is made of polyurethane and forms 35-85% of the volume ofthe lifter bar and the first portion of the lifter bar body is made ofrubber or the first portion of the lifter bar body is made of otherpolyurethane than the polyurethane in the second portion of the lifterbar body.

The shell plate comprises a shell plate body which has a first portioncomprising a fixing surface for fixing the shell plate body to the shelland a second portion comprising a wear surface facing toward interior ofthe grinding mill, said first portion and said second portion forming acontinuous shell plate body. The second portion comprises polyurethanesuch that the wear surface is made of polyurethane.

The polyurethane in the context of this application means polyurethanematerial that may comprise additives, such as metal particles, ceramicsor carbide. The polyurethane material comprises at least 50% andpreferably at least 80% pure polyurethane the rest being additives andpossible impurities.

The polyurethane may comprise additives, such as metal particles,ceramics or carbide.

In one embodiment of the shell plate the second portion is made ofpolyurethane.

In another embodiment of the shell plate the first portion is made ofpolyurethane.

In still another embodiment of the shell plate the first portion is madeof recycled polyurethane.

In still another embodiment of the shell plate the second portion ismade of more wear resistant polyurethane than the first portion.

In an embodiment of the shell plate the first portion comprises rubber.In another embodiment of the shell plate the first portion is made ofrubber. The rubber may be recycled rubber.

Between 40 to 80%, preferably between 45 to 70%, of the second portionof the shell plate body is polyurethane. The shell plate has a thicknessbetween 3 to 20 cm, preferably between 4 to 15 cm.

Method for making a shell plate as described earlier comprises steps ofproviding a mould for moulding the shell plate, adding polyurethane intothe mould for forming the shell plate body. The polyurethane is in sucha state that it is arranged to react in the mould and form a connectionwith a material of the first portion of the shell plate body and addingmaterial into the mould for forming the first portion of the shell platebody such that the polyurethane is arranged to react in the mould withthe material for forming a continuous shell plate body with the secondportion of the shell plate body. Shell plates can be made with mouldsmade of sheet metal having a thickness between 0.1 to 10 mm, preferablyless than 5 mm and most preferably 0.2-2 mm.

In an embodiment of the method the step of adding material into themould comprises adding material other than the polyurethane of thesecond portion into the mould for forming the first portion of the shellplate body.

In another embodiment of the method the step of adding material into themould comprises adding polyurethane into the mould for moulding thefirst portion of the shell plate body.

When arranging polyurethane into the mould the polyurethane is in such astate that it is arranged to react in the mould and form a connectionwith a material of the first or the second portion of the shell platebody.

The first portion of the shell plate body may be the same material asthe second portion of the shell plate body or it may be differentmaterial than the second portion, for example rubber, recycled rubber orpolyurethane having different properties than the polyurethane in thesecond portion of the shell plate body. The method may further comprisea step of adding other material than the polyurethane of the secondportion into the mould for forming the first portion of the shell platebody, the material of the first portion is in such a state that it isarranged to react in the mould such that the polyurethane in the secondportion and the material in the first portion form a connection witheach other for forming a continuous shell plate body.

In still another embodiment of the method the mould has an interiorspace and the step of adding material into the mould comprises addingmaterial in a form of providing a base member. In this embodiment themethod further comprises the steps of joining the mould and the basemember together to form a cavity defined by the base member and theinterior space; and the step of adding polyurethane comprises adding thepolyurethane to fill the cavity with polyurethane.

Effect of a shell plate comprising polyurethane is that the polyurethaneneeds less pressure and heat than other materials, such as rubber, andenergy consumption can be reduced in manufacturing. Also themanufacturing process is easier because shell plate comprisingpolyurethane can be made using mould made from sheet metal. The shellplates can be retreated with new polyurethane when the wear surface hasworn away. This retreatment can be made in smaller scale near to thefactory so the need for transportation is less.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be described in greater detail bymeans of preferred embodiments with reference to the attached drawings,in which

FIG. 1 shows a grinding mill;

FIG. 2 shows a cross section of the grinding mill in FIG. 1;

FIG. 3 shows a shell plate; and

FIGS. 4a, 4b and 4c show embodiments of a shell plate.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a longitudinal cross-section of a horizontal grinding mill3 having an inner shell 2 comprising a cylindrical wall which the shell2 comprises lifter bars 11 mounted to the cylindrical wall of the shell2 and in between the lifter bars 11 there are shell plates 1. Thegrinding mill 3 rotates about its central axis x in a predetermineddirection. The axis of the shell 2 is horizontally disposed or slightlyinclined toward the other end of the shell 2. The surface of the innershell 2 is plated with shell plates 1 for protecting the drum againstwear caused by grinding. The shell plates 1 is attached between thelifter bars 11 such that the lifter bars 11 and the shell plates 1together protect the surface of the inner shell 2 of the grinding mill3.

FIG. 2 shows a cross-section of the grinding mill 3 shown in FIG. 1taken along line A-A. The grinding mill 3 rotates in a predetermineddirection around its axis indicated by x. The shell plates 1 and thelifter bars 11 are arranged such that they are mounted to the shell 2 ofthe grinding mill 3 extending in the longitudinal direction of thehorizontally arranged grinding mill 3. The shell plate 1 is secured tothe shell 2 of the grinding mill 3 with fasteners such as boltsextending from the shell 2 of the grinding mill 3 to a fixing elementembedded to the shell plate 1 or the shell plate 1 is secured with aninterlocking effect provided by adjacent lifter bars 11.

The shell plate 1 has the same or substantially same degree of curvatureas the shell 2 of the grinding mill 3. The curvature is especially onthe fixing surface 13 of the shell plate 1 but the same or similarcurvature may be also on the wear surface 12 of the shell plate 1.

The shell plate 1 may be made of polyurethane such that the whole shellplate 1 is made of same polyurethane or the shell plate 1 may compriserubber, which is preferably but not necessarily recycled rubber, andpolyurethane such that the polyurethane forms at least part of the wearsurface 12 of the shell plate 1, or the shell plate may comprisepolyurethane such that at least the wear surface 12 comprises newpolyurethane and the rest of the shell plate 1 comprises recycledpolyurethane or other polyurethane than that of the polyurethane in thewear surface 12. The difference in polyurethanes comes from differentproperties in polyurethane, such as additives.

The polyurethane may comprise additives, such as metal particles,ceramics or carbide. The parts of the shell plate body that are formedby polyurethane are mostly polyurethane and if there are the additives,the additives form smaller part than the polyurethane.

FIG. 3 shows a shell plate 1 together with the adjacent lifter bars 11arranged to a shell 2 of a grinding mill. The shell plate 1 comprises ashell plate body 10 which is divided into a first portion 10 acomprising a fixing surface 13 for fixing the shell plate body 10 to theshell 2 and into a second portion 10 b comprising a wear surface 12facing toward interior of the grinding mill 3. The first portion 10 aand the second portion 10 b form a continuous shell plate body 10. Atleast part of the shell plate body 10 comprises polyurethane. Thedivision into the first portion 10 a and into the second portion 10 b isimaginary when the shell plate body is completely made of polyurethane.When the shell plate body 10 comprises different materials for examplesuch that polyurethane forms the second portion 10 b of the shell platebody 10 and rubber forms the first portion 10 b of the shell plate body10 then the division is according to the materials.

The shell plate 1 is in this embodiment mounted to the shell 2 of thegrinding mill with an interlocking effect by adjacent lifter bars 11.The shell plates 1 are first arranged against the shell 2 and then thelifter bars 11 are arranged such that part of the lifter bars 11 are ontop of the side of the shell plates 1 so that part of the shell plate 1is compressed between the shell 2 and the lifter bar 11 when the lifterbar 11 is secured to the shell with fixing means.

FIG. 4a shows an embodiment of a shell plate 1 completely made ofpolyurethane. The completely means that the complete shell plate body 10having a first portion 10 a and a second portions 10 b is made ofpolyurethane but the polyurethane may comprise additives as earlierdescribed. The shell plate body 10 is now imaginarily dived into thefirst portion 10 a and into the second portion 10 b because the wholeshell plate body 10 is of one material. The second portion 10 bcomprises a wear surface 12 and the first portion 10 a comprises afixing surface 13.

FIG. 4b shows an embodiment of the shell plate 1 comprising onlypolyurethane. First example of the embodiment shown in FIG. 4b is suchthat the first portion 10 a is made of polyurethane and the secondportion 10 b is made of other polyurethane than that of the firstportion 10 a. The polyurethane in the first portion 10 a and thepolyurethane in the second portion 10 b have different properties. Thedifference in properties may be for example such that the polyurethanesin different portions have difference in wear resistance for examplesuch that the difference in wear resistance is 10%. Another example ofthe embodiment shown in FIG. 4b is such that the first and the secondportion 10 a, 10 b both are made of the same polyurethane but they aremade at different times, i.e. not simultaneously. The other polyurethanemay be for example recycled polyurethane.

FIG. 4c shows an embodiment of a shell plate 1 comprising a firstportion 10 a made of rubber and a second portion 10 b made ofpolyurethane. The first portion 10 a made of rubber may be made ofrecycled rubber.

The curvature of the shell plates 1 are exaggerated in FIGS. 4a-4c andin reality they are much less curved. Radius of the outer surface of thefirst portion could be for example between 0.3-10 m. Radius of the outersurface of second portion could be at least 0.3 m, preferably 0.3 m-10m. The outer surface of the second portion could even be straight. Theouter surface of the second portion 10 b is the wear surface 12 of theshell plate 1 which is toward the interior of the grinding mill and theouter surface of the first portion 10 a is the fixing surface 13. Theshell plates 1 are 3-20 cm thick, preferably 4-15 cm, for example 10 cm.The shell plates 1 comprise polyurethane 40-80% and preferably 45-70%.

It will be obvious to a person skilled in the art that, as thetechnology advances, the inventive concept can be implemented in variousways. The invention and its embodiments are not limited to the examplesdescribed above but may vary within the scope of the claims.

1. A shell plate mountable to a shell of a grinding mill for grindingore, said shell plate comprises a shell plate body having a firstportion comprising a fixing surface for fixing the shell plate body tothe shell and a second portion comprising a wear surface facing towardinterior of the grinding mill, said first portion and said secondportion forming a continuous shell plate body, the second portioncomprises polyurethane such that the wear surface is made ofpolyurethane and the first portion is made of rubber.
 2. A shell plateaccording to claim 1, wherein the second portion is made ofpolyurethane.
 3. (canceled)
 4. (canceled)
 5. (canceled)
 6. A shell plateaccording to claim 1, wherein the polyurethane comprises additives, suchas metal particles, ceramics or carbide.
 7. (canceled)
 8. (canceled) 9.A shell plate according to claim 7, wherein the rubber is recycledrubber.
 10. A shell plate according to claim 1, wherein 40-80%,preferably 45-70%, of the second portion of the shell plate body ispolyurethane.
 11. A shell plate according to claim 1, wherein the shellplate has a thickness of 3-20 cm, preferably 4-15 cm.
 12. Method formaking a shell plate according to claim 1, the method comprising thesteps of: providing a mould for moulding the shell plate; addingpolyurethane into the mould for forming the second portion of the shellplate body, the polyurethane is in such a state that it is arranged toreact in the mould and form a connection with a material of the firstportion of the shell plate body; and adding material into the mould forforming the first portion of the shell plate body such that thepolyurethane is arranged to react in the mould with the material forforming a continuous shell plate body with the second portion of theshell plate body.
 13. Method according to claim 12, wherein the step ofadding material into the mould comprises adding material other than thepolyurethane of the second portion into the mould for forming the firstportion of the shell plate body.
 14. Method according to claim 12,wherein the mould having an interior space and the step of addingmaterial into the mould comprises adding material in a form of providinga base member; the method further comprising the steps of: joining themould and the base member together to form a cavity defined by the basemember and the interior space; and the step of adding polyurethanecomprises adding the polyurethane to fill the cavity with polyurethane.15. A grinding mill for ore grinding comprising multiple shell platesarranged to a shell of the grinding mill, said shell plates areaccording to claim
 1. 16. A grinding mill according to claim 15, whereinthe grinding mill having grinding energy per ton of ore of 1-30 kWh/tand preferably 3-20 kWh/t.
 17. A grinding mill according to claim 15,wherein the grinding mill having a diameter of 1-15 m, preferably 1.5-10m.
 18. A grinding mill according to claim 15, wherein the grinding millhaving a length of 1-15 m in horizontal direction, preferably 2-8 m. 19.A grinding mill according to claim 15, wherein the shell of the grindingmill having a thickness of 0.5-10 cm.
 20. A grinding mill according toclaim 15, wherein the grinding mill comprises multiple lifter barsarranged to the shell, the lifter bars comprise a lifter bar body havinga fixing surface for fixing the lifter bar to the shell and a wearsurface facing toward interior of the grinding mill, the wear surface ofthe lifter bars and the wear surface of the shell plates comprisepolyurethane.
 21. A grinding mill according to claim 15, wherein saidgrinding mill is arranged to grind input material of which at least 80%has particle size between 0.1-300 mm, preferably 1-250 mm and mostpreferably 80-220 mm to grinded output material of which 80% hasparticle size between 0.02-3 mm, preferably 0.05-2.5 mm and mostpreferably 0.2-2 mm.
 22. A grinding mill according claim 15, wherein thegrinding mill comprises a lifter bar arranged to the shell, the lifterbar having a volume, the lifter bar further having an outer surfacecomprising a fixing surface to be arranged against the shell and a wearsurface facing toward interior of the grinding mill, the lifter barcomprises a lifter bar body having an outer surface conforming the outersurface of the lifter bar and a fixing element for connecting the lifterbar to the shell of the grinding mill, the lifter bar body furthercomprising a first portion and a second portion forming a continuouslifter bar body, the fixing element is embedded to the first portionsuch that it forms part of the fixing surface of the lifter bar, thesecond portion is made of polyurethane and forming 35-85% of the volumeof the lifter bar and the first portion of the lifter bar body is madeof rubber or the first portion of the lifter bar body is made of otherpolyurethane than the polyurethane in the second portion of the lifterbar body.
 23. Use of a grinding mill for grinding ore comprising atleast one shell plate according to claim
 1. 24. Use according to claim23, wherein the grinding energy per ton of ore is 1-30 kWh/t andpreferably 3-20 kWh/t.